Electrostatic precipitators have a wide range of uses. Electrostatic precipitators are often used in many applications including power generating stations to collect products of combustion from a boiler before the products of combustion are exhausted to the surrounding atmosphere. Typically, electrostatic precipitators include a plurality of collector plates or curtains. The products of combustion passing the plates will deposit solids on the plates. In addition, the electrostatic precipitators have wires or discharge electrodes positioned between the plates. The discharge electrodes are electrically charged so that products of combustion passing the discharge electrodes become charged with one charge and are attracted to the collector plates. In the course of operation, it is common for material to collect on both active elements, that is, the discharge electrodes and the collector plates. A customary method of removing material from the active elements is to vibrate those elements so that material adhering to the elements is dislodged and falls to the bottom of the electrostatic precipitator where it is collected. A widely accepted method of vibrating the elements is to apply an impact force to the element to generate vibration in the element. The apparatus for applying the impact force is generally known as a rapper or a vibrator.
Typically, rappers are connected to an element of the precipitator through metal supports. In the event that an element of the precipitator is at a high voltage, at least a portion of the rapper is at the same voltage as the element to which the rapper is connected. This requires that the active portion of a rapper in electrical contact with a high voltage element of the precipitator be electrically insulated from another portion of the rapper which drives the active portion.
In many instances, it is necessary to adjust the active portion of the rapper in order to adjust the amount of impact force which is applied to the selected portion of a precipitator. It is desirable to be able to make an adjustment of the impact force without interrupting the electricity which is applied to the high voltage element of the precipitator.